The Next ticketing system is a good idea for Achatz because it eliminates an obstacle to purchasing tickets: the near total uncertainty as to when you might get a table. A seating for 4 people at Alinea might require a month or two advance notice; a prime date perhaps even more. So it's a win to be able to look at a website and see when you might be able to get a table --- or, with the new Sicily menu, quickly discover that there are no seatings to be had.

Incidentally, if you're hoping for last minute seatings, there's always the strategy of just calling them at the last minute or even just showing up to see if they've had cancellations. I've gotten lucky at least once.